Long-term verbal memory deficit and associated hippocampal alterations in 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a genetic disease associated with an increased risk for schizophrenia and a specific cognitive profile. In this paper, we challenge the current view of spared verbal memory in 22q11.2DS by investigating verbal memory consolidation processes over an extended time span to further qualify the neuropsychological profile. Our hypotheses are based on brain anomalies of the medial temporal lobes consistently reported in this syndrome. Eighty-four participants (45 with 22q11.2DS), aged 8-24 years old, completed a verbal episodic memory task to investigate long-term memory on four different time delays. We compared trajectories of forgetting between groups (22q11.2DS vs. controls) and analyzed performance inside the 22q11.2DS sample through cluster analyses. Potential links between memory performance and volume of the hippocampal subfields were examined. We showed accelerated long-term forgetting (ALF) in the 22q11.2DS group, visible after a delay of one day. Using mixed models, we showed significant differences in the shape of memory trajectories between subgroups of participants with 22q11.2DS. These sub-groups differed in terms of memory recognition, intellectual functioning, positive psychotic symptoms and grey matter volume of hippocampal subfields but not in terms of age. In conclusion, by investigating memory processes on longer delays than standardized memory tasks, we identified deficits in long-term memory consolidation leading to ALF in 22q11.2DS. Nevertheless, we showed that a subgroup of patients had larger memory consolidation deficit associated with lower intellectual functioning, higher rates of positive psychotic symptoms and hippocampal alterations.